The present invention relates to a high power control system and a control method thereof, and more particularly, to a high power control system for converting a DC output of a high power battery into an AC output and a control method thereof.
Due to exhaustion of fossil fuel, attempts to use new regeneration energy such as sunlight and wind have been gradually increased. Furthermore, in order to efficiently use generation facilities, generated energy may not be directly used, but stored in a battery so as to be utilized during a peak load.
As the power of new regeneration energy or energy stored in a battery is increased to high power, for example, 500 kW or 1 MW, the capacity of an inverter to convert the energy has been also increased. In order to drive a high power inverter, a lot of elements must be considered.
FIG. 1 is a block configuration diagram of a conventional energy storage device including one inverter. In the energy storage device, one controller controls one inverter. Such a structure has high total harmonic distortion (THD) and high input current ripple. Furthermore, when the inverter is broken down, power supply may be stopped, and a low mean time between failure (MTBF) may degrade the reliability of the system may be degraded, and increase the maintenance cost.
In order to solve such problems, a method of controlling a plurality of inverters in parallel has been proposed.
FIG. 2 is a block configuration diagram of a conventional energy storage device including a plurality of parallel inverters. In the energy storage device, one controller controls a plurality of parallel inverters. In such a structure, when one inverter is broken down, a spare inverter may be used to drive the energy storage device. Thus, power supply may not be stopped, but the broken inverter may be easily replaced to thereby make it easier to maintain the system. In this case, however, since a circulating current flows among inverters, the inverters cannot be operated in a state where a load is assigned to the inverters. Furthermore, since the inverters cannot be independently controlled, the inverters cannot be circularly activated. Thus, since it is difficult to expect high MTBF, the reliability of the system may be degraded. Furthermore, since the parallel inverters are operated at the same time, the energy storage device cannot satisfy THD required by a battery during a low-load condition, and cannot secure low input current ripple.